There are 4 ways to translate the website:

1. Translate interface (this has everything that needs to be translated)
2. Structure (translating the structural component... pinpointing the exact spot of a word/phrase that needs translation)
3. View (basically the list of everything that meets a certain criteria) Handle with caution.
4. String overrides (the nuclear option; your last resort) Handle with caution.

You should start with 1 & 2 if possible. There will be times where you think you've translated something successfully only to find that even after you've flushed the caches, it doesn't seem to work. In which case, you'll have to dive deeper and go to option 3 (View). 

We only use 4 (String overrides) if you have a word like "lesson" and you know that the only context it is ever written in on our site is the most commonly used meaning of the word. In this case, you can just translate it on the whole site at once using the string override. Otherwise, you can't touch this.